1. Field of the Invention
The present invention relates to a connecting structure for covered wires where their respective conductors are connected to each other by oscillating respective insulating covers of the wires with ultrasonic waves. More particularly, it relates to a connecting structure which is effective to connect a shield wire with a ground wire.
2. Description of the Related Art
Generally speaking, it is complicated and troublesome to handle a shield wire having a braided wire coaxially disposed around a core line (or core lines) with the deteriorated workability in using the shield wire. As an effective measure for improving the deteriorated workability, there is provided a connecting structure for wires which takes advantage of inside heating due to the ultrasonic oscillation by Japanese Unexamined Patent Publication (kokai) No. 7-320842.
In the publication, there are shown two kinds of covered wires. One is a shield wire which comprises a core line, an inside insulating rind arranged outside the core line, a braided wire as a shield conductor arranged outside the inside insulating rind, and an outside insulating rind. The other is a ground wire consisting of a core line and an outside resinous rind arranged outside the core line.
According to the disclosed method of connecting the braided wire of the shield wire being connected to a connector, to the core line of the ground wire being also connected to the connector, in front of the connector, the ground wire is firstly overlaid on the shield wire so as to cross each other at a connection point. Next, the overlapping portions are interposed between upper and lower resin tips. Then, while compressing the upper and lower resin tips from the outside, they are subjected to ultrasonic oscillation by making use of an ultrasonic horn and an anvil. Consequently, both of the outside rinds of the shield wire and the ground wire are molten for elimination, so that the braided wire of the shield wire comes into electrical contact with the core line of the ground wire. Simultaneously, the upper and lower resin tips are mutually welded to each other thereby to seal up the surroundings of the above connecting point. Note, in the modification, there is a case that the upper and lower resin tips are respectively provided, on bearing faces thereof, with wire-accommodating shallow grooves for positioning the shield wire.
In the above-mentioned connecting structure, however, there is sometimes observed a phenomenon that, when welding the upper and lower resin tips to each other, the outside insulating rind of the shield wire is disadvantageously torn or broken in the vicinity of a point where the periphery of the upper resin tip abuts on the shield wire, so that the braided wire of the shield wire is exposed outside the integrated tips. In such a case, the exposure of the braided wire causes the fixing force between the integrated resin tips and the shield wire, i.e. the strength of connection, to be reduced, also lowering the insulating effect brought by the integrated tips.
Under such a circumstance, it is therefore an object of the present invention to provide a connecting structure for covered wires, which is capable of improving the strength in connection and the insulating effect.
The object of the present invention described above can be accomplished by a connecting structure for covered wires, comprising:
a first covered wire having a first conductor covered with a first resinous cover;
a second covered wire having a second conductor covered with a second resinous cover, the second conductor being electrically connected with the first conductor of the first covered wire cross each other; and
an upper resin tip and a lower resin tip between which an electrical connecting part of the first and second conductors and the surroundings are interposed, the upper resin tip being welded to the lower resin tip while interposing the first and second covered wires between the upper resin tip and the lower resin tip;
wherein each of the upper and lower resin tips is provided, on its butt face being abutted against the other resin tip, with a wire receiving groove which has a semi-circular cross section of a diameter corresponding to the diameter of the first covered wire.
According to the connecting structure, since the diameter of the wire receiving groove corresponds to the diameter of the first covered wire, it is possible to weld the upper resin tip to the lower resin tip in the wrapping manner without compressing the first resinous cover of the first covered wire. Thus, since there is no possibility that the first resinous cover of the first covered wire is torn or broken by the upper or lower resin tip, the fixing force between the upper and lower resin tips and the first covered wire can be enhanced. In addition, it is possible to exclude a possibility that the first covered wire exposes the first conductor in the vicinity of the upper and lower resin tips. In the above-mentioned connecting structure, preferably, the first covered wire is a shield wire, while the second wire is a ground wire and wherein the first conductor is a shield conductor of the shield wire, while the second conductor is a core line of the ground wire.
According to the above-mentioned constitution, it is possible to weld an outside rind of the shield wire in the wrapping manner, whereby the damage on the outside rind can be prevented. Thus, owing to the reduced damage on the outside rind, the fixing force between the upper and lower resin tips and the shield wire can be enhanced to stabilize the connecting strength.
In the above-mentioned connecting structure, preferably, the upper resin tip is provided, at an intermediate portion of the wire receiving groove in the longitudinal direction, with a press part which serves to urge the second covered wire against the first covered wire and of which depth is smaller than the other portion of the wire receiving groove.
According to the above-mentioned structure, owing to the provision of the press part, it is possible to compress the overlapping portions of the covered wires intensely. Thus, it is possible to accelerate the progress of melting and welding. Moreover, since the provision of the press part allows the resultant connecting structure to restrict a portion where the first and second resinous covers are to be removed by the ultrasonic oscillation, it is possible to accomplish the stable electrical connection between the covered wires, thereby improving the reliability of electrical connection. Further, owing to the concentration of ultrasonic waves on the press part, it is possible to reduce the welding energy itself.
In the above-mentioned connecting structure, preferably, each of the upper and lower resin tips is provided, on an outer edge of the butt face, with a recess for fitting the second resinous cover of the second covered wire.
According to the above-mentioned structure, when abutting the upper resin tip against the lower resin tip, it is possible to accommodate the second resinous cover of the second covered wire in the recess in the wrapping manner. Thus, it is possible to hold the second covered wire securely and prevent the second conductor of the second covered wire from being exposed, whereby the insulating effect can be enhanced. Additionally, since the second covered wire is welded in a manner that the upper and lower resin tips envelop the leading end of the second resinous cover of the second covered wire, it is possible to enhance the waterproof capability of the second covered wire at the leading end.
In the above-mentioned connecting structure, preferably, the upper resin tip is provided, on a part of the butt face contacting the second covered wire, with a protrusion for concentrating an ultrasonic energy in oscillating the upper and lower resin tips with ultrasonic waves.
According to the above structure, owing to the provision of the protrusion, it is possible to concentrate the ultrasonic energy on a part of the second covered wire in contact with the protrusion, so that the second resinous cover of the second covered wire can be molten initially and thereafter, the butt faces of the upper and lower resin tips can be welded to each other. Thus, it is possible to weld the second covered wire to the first covered wire certainly, whereby the welding strength can be improved. Further, owing to the concentration of ultrasonic waves on the protrusion, it is possible to reduce the energy loss, thereby allowing the welding period to be reduced.
According to the present invention, there is also provided a method of producing a connecting structure for covered wires, the method comprising the steps of:
preparing a first covered wire having a first conductor covered with a first resinous cover and a second covered wire having a second conductor covered with a second resinous cover;
overlaying the second covered wire on the first covered wire cross each other;
interposing respective overlapping portions of the first and second covered wires between an upper resin tip and a lower resin tip; and
oscillating the upper and lower resin tips with ultrasonic waves while compressing the upper and lower resin tips from the outside, whereby the first and second resinous covers of the first and second covered wires are molten for removal thereby to bring the first conductor of the first covered wire into electrical contact with the second conductor of the second covered and simultaneously, the upper and lower resin tips are mutually welded to each other thereby to seal up the surroundings of a contact between the first conductor and the second conductor;
wherein each of the upper and lower resin tips is provided, on its butt face being abutted against the other resin, with a wire receiving groove which has a semi-circular cross section of a diameter corresponding to the diameter of the first covered wire.
Also in the above-mentioned method, preferably, the first covered wire is a shield wire, while the second wire is a ground wire and wherein the first conductor is a shield conductor of the shield wire, while the second conductor is a core line of the ground wire.
In the above-mentioned method, preferably, the upper resin tip is provided, at an intermediate portion of the wire receiving groove in the longitudinal direction, with a press part which serves to urge the second covered wire against the first covered wire and of which depth is smaller than the other portion of the wire receiving groove.
In the above-mentioned method, preferably, each of the upper and lower resin tips is provided, on an outer edge of the butt face, with a recess for fitting the second resinous cover of the second covered wire.
In the above-mentioned method, preferably, the upper resin tip is provided, on a part of the butt face contacting the second covered wire, with a protrusion for concentrating an ultrasonic energy in oscillating the upper and lower resin tips with ultrasonic waves.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawings.